java - Add Images using Spinner in Android Studio -


i'm trying load image in mainactivity based on selected spinner element.

so if spinner consist 2 channel names in layout, , these names stored in array channels = ["skysports", "premierlive"]

i have defined imageview:

imageview logo = (imageview) findviewbyid(r.id.logo);

while creating spinner i'm using channels array , there i'm calling 

getlogo(channels[i]);

where channels[i] current selected spinner element.

finally, i'm trying implement image switch switch-case inside getlogo:

public void getlogo(string channel){         switch(channel){             case ("skysports"):                 logo.setimageresource(r.drawable.skysports);                 break;             case ("premierlive"):                 logo.setimageresource(r.drawable.premierlive);                 break;         }     }

all gives me

java.lang.nullpointerexception: attempt invoke virtual method 'void android.widget.imageview.setimageresource(int)' on null object reference

what shall do? tnx

edit:

activity_main:

    <relativelayout xmlns:android="http://schemas.android.com/apk/res/android"         xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"         android:layout_height="match_parent" android:paddingleft="@dimen/activity_horizontal_margin"         android:paddingright="@dimen/activity_horizontal_margin"         android:paddingtop="@dimen/activity_vertical_margin"         android:paddingbottom="@dimen/activity_vertical_margin" tools:context=".mainactivity">       <spinner             android:layout_width="fill_parent"             android:layout_height="wrap_content"             android:id="@+id/spinnermain"             android:paddingleft="30dp"             android:paddingright="10dp"             android:paddingtop="2dp"             android:paddingbottom="2dp"             android:clickable="true"             android:touchscreenblocksfocus="true"             android:layout_alignparenttop="true"             android:visibility="visible"             android:textsize="@android:dimen/app_icon_size"             android:layout_centervertical="true"             android:layout_alignparentleft="true"             android:layout_alignparentstart="true"          <imageview             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:id="@+id/logo"             android:layout_centerhorizontal="true"             android:layout_margintop="20dp" />  </relativelayout>

and mainactivity:

   public class mainactivity extends actionbaractivity implements view.onclicklistener {         string[] channels;         string channel;         spinner sp;         imageview logo;   protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         imageview logo = (imageview) findviewbyid(r.id.logo);          sp = (spinner) findviewbyid(r.id.spinnermain);         addspinner();   public void addspinner(){         channels = getchannels();         arrayadapter<string> adapter = new arrayadapter<string>(this, r.layout.spinner_item, channels);         sp.setadapter(adapter);         sp.setonitemselectedlistener(new adapterview.onitemselectedlistener() {             public void onitemselected(adapterview<?> parent, view view, int position, long id) {                 int index = parent.getselecteditemposition();                 getlogo(channels[index]);                    }          });    }     }

}

i ser in activity private field logo , in oncreate method local variable called logo variable initialized. in oncreate method need initialize private field used in other methods of class, rather have

imageview logo = (imageview) ...

you should have 

logo = (imaview) ...

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